/**
 * Copyright [2012-2013] [Guðmundur Björn Birkisson]
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License. Copyright [2012-2013] [Guðmundur Björn Birkisson]
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * ---------------------------------------------------------------------------
 * 
 * Class name:  CommandList
 * 
 * Description of class:
 * 
 * Simple linked list that stores commands executed to allow undo/redo.
 * 
 */

package karel.editors.mapeditor;


public class CommandList {

    private class Node {
        public Node prev;
        public Node next;
        public Command c;
    }
    
    private Node current;
    
    public CommandList() {
        current = new Node();
    }
    
    public void addCommand(Command c) {
        Node n = new Node();
        n.c = c;
        n.prev = current;
        current.next = n;
        current = n;
        c.execute();
    }
    
    public void undo() {
        current.c.unexecute();
        current = current.prev;
    }
    
    public void redo() {
        current = current.next;
        current.c.execute();
    }
    
    public boolean canUndo() {
        return current.c != null;
    }
    
    public boolean canRedo() {
        return current.next != null;
    }
}
